1. Field of the Invention
The present invention concerns a blood pump used for artificial heart-lung machine or the like, and more particularly, a centrifugal pump that can be operated with the rotation shaft out of contact in respect to the bearing by controlling the rotating speed.
2. Detailed Description of the Prior Art
Recently, studies for replacing or complementing a malfunctioning internal heart with an artificial heart have been conducted vigorously in Japan and abroad in past several decades. As important problems for the practical use of artificial heart, first, we can name the prevention of thrombosis from occurring in the artificial heart. In addition, improvement of durability of artificial heart is also an essential problem to be resolved for the practical use thereof.
Initially, the research and development of artificial heart have been conducted mainly for pulsation type pumps such as bellows pump or the like having pulsation function similar to the human heart; however, in recent years, a continuous flow type centrifugal pump without pulsation attracts attention, because the miniaturization is easy, and moreover, the structure is simple and the durability is excellent.
In short, various research and development are being conducted concerning the centrifugal pump, because it has been demonstrated that the centrifugal pump is appropriate for use as complementary means of an original heart by disposing in the body in parallel with the original heart, because it can be reduced easily in size and weight, or, that the organism can cope with the fluid transferred by the pump even if the fluid is continuous, thanks to physiological factors of the human body, or others.
For example, in Japan, an external auxiliary circulating pump using a centrifugal pump, having cleared the legal review, is in the phase of practical use. This external auxiliary circulating pump, supposing a usage duration of one month or less, the occurrence of thrombosis is not so problematic.
On the other hand, researches for practical use of pulsation type pump are active, and 7 clinical examples of integral implantation of artificial heart with pulsation type pump have been reported in 2001.
Nonetheless, it is difficult to miniaturize the pulsation type artificial heart and, consequently, the pulsation type artificial heart is limited to the application for adults of 85 Kg or more in weight. On the contrary, the continuous flow artificial pump with centrifugal pump can be miniaturized easily and has an advantage that it is not particularly necessary to limit physically patients to whom it is applied.
A number of prior arts have been disclosed, concerning the continuous flow type blood pump by a centrifugal pump; however, actually, it can not be the that the following two problems are solved for a prolonged use.
Namely:
(a) Control of thrombosis occurrence.
(b) Sustention of stable rotation by preventing the rotation shaft from wear in the bearing section.